Hiding behind the mesmerizing power of identity politics, in this case multiplied by two, the left is about to capture America by stealth. Senators Clinton and Obama are the perfect agents. She is a born meddler, a political Dolly Levy who can hardly wait to start arranging our lives. He does magic tricks, especially illusions, and with that qualification, is now anxious to experiment with America’s future.

Neither of them is high on America. Mr. Obama seems to take an especially jaundiced view. Both intend to transform America into something else.

The left has been trying to transform America for decades — and not without some success. Yet America is still too much of a meritocracy. Its economy is too competitive and too productive. Too many people are too affluent, too independent, and too hard for government to control. Most of us are also too religious, especially in the predominant Judeo-Christian tradition that emphasizes individual responsibility and achievement more than group identity. If the left is to change America fundamentally, instead of just wounding it severely, Mrs. Clinton and Mr. Obama will need a bigger weapon. That is a “change” about which they dare not speak.

In addition to public ownership, which doesn’t work, and the Democrats’ standard formula of higher taxes and spending, which is destructive, the inevitable next step is to add a system of “mandates.” Under this mutation, government allows for the continuation of private property and businesses, but only in modified form. Government selectively intervenes to direct how property is used or a business is run — and, to the extent it wishes, to require selected people to use their time, talents, and energies as directed.

Government mandates can be used to tell businesses what products to produce, loans to make, news to report, wages to pay, employees to hire, fringe benefits to provide, customers to serve, prices to charge, stockholders to have, and dividends to distribute. Life-cycle instructions for individuals often include school, neighborhood, job, marriage, child rearing, medical care, religion, speech, political activity, and inheritance.

The power of mandates to accomplish transformational change is enormous. For example, each company that does business with the federal government can be required to: (i) maintain a satisfactory “scorecard” that measures its compliance with mandates and (ii) refrain from hiring or doing business with anyone that does not also have a satisfactory scorecard. Needless to say, everyone who wishes to remain in business or have a job must quickly fall in line.

The worldwide trend is toward greater use of mandates, as even democratically elected governments seek to extend their reach far beyond the traditional functions of taxing and spending. Why not simply skip the intermediate steps and assign tasks directly to the private sector?

Left-wing regimes in the E.U. add to their welfare systems by requiring private sector employers variously to provide maternity benefits, often to both sexes, child care, education, and a broad range of other supplements. France mandates the retention of bad employees and redundant jobs.

The government in South Africa has used a scorecard-type system of mandates called Black Economic Empowerment in forcing all companies to have a substantial contingent of black owners, as well as specified percentages of black managers and employees.

In Britain, even the Tories are talking about imposing a “responsibility index” system which makes companies use their stockholders’ money to achieve social and other goals specified by government.

In a similar way, one of Mr. Obama’s opening proposals is to punish companies if they do not maintain government-prescribed levels of employment, provide specified pensions, and have the right “attitudes” toward labor unions.

Mrs. Clinton is a big package of mandates waiting to happen, not just in health care and family life, but also across the board. One can only imagine what a full list of government mandates will look like if the left manages to get either of its candidates elected on a platform of “change.”

The political power of mandates is great. The left has already broken America’s melting pot, in the name of “diversity,” and is now pushing to create more identity-group classifications.

Mandates are the perfect tool. First they can magnify existing gender and racial preferences. Then they can be used to provide many more identity groups with their own sinecures and special relationships with government. Thus fortified, identity groups can sustain a left-wing political coalition strong enough to rule America for the foreseeable future.

With the left at the helm, mandates imposed in the name of saving the environment or meeting new challenges from globalization, or simply in the name of change, almost certainly will be used to commandeer labor and capital resources to a degree not experienced in this country since the dangerous days of the Great Depression and World War II.

Mr. Christian, a veteran Washington lawyer, is writing a book about the abuse of federal power.